This invention generally relates to systems in which a belt interacts with a pulley (some technologies refer to pulleys as sheaves). More particularly, this invention relates to systems, such as lifting devices or power transmission devices (e.g. drive belts) in which the interaction between the belt and the pulley may produce undesired noise.
Elevator systems are one example of the aforementioned lifting devices. Some elevator systems are traction elevator systems that use one or more belts to support and/or provide a lifting force to the elevator car and/or the counterweight. The belts can comprise a plurality of tension members, such as cords formed from steel wire, within a jacket, such as a polymer. The belts route around one or more sheaves of the elevator system, typically made of metal, to perform these functions.
These elevator systems rely upon sufficient traction between a sheave driven by the elevator machine (referred to as a drive sheave and/or traction sheave) and the belt for several reasons. First, sufficient traction ensures that the belt moves along with the drive sheave during rotation of the drive sheave by the elevator machine in order to achieve the desired movement of the car and/or counterweight. Second, sufficient traction ensures that the belt does not move relative to the drive sheave when the drive sheave is not rotating in order to keep the elevator car at a desired position (e.g. when the elevator car is at a landing).
These elevator systems may also include one or more other sheaves that help guide the belt around various components of the elevator system in a desired arrangement (referred to as deflector sheaves, idler sheaves and/or diverter sheaves).
Under certain conditions, the belt could slip relative to the sheave. This slip condition could produce an undesired noise. The undesired noise could be airborne (e.g. travelling through the air in the hoistway) or structure borne (e.g. travelling along the belt to other components of the elevator system).
A variety of approaches have been proposed for reducing or eliminating such noise. Most of those efforts have focused on the belt. Exemplary approaches include using a different jacket material, adjusting the wax content in the jacket material, or periodically conditioning the installed belt (e.g. applying a wax to the jacket).